There are various types of machines for spreading fertilizer, such as compost, manure, lime, commercial fertilizer, and the like, onto lawns, gardens and fields. One type is commonly referred to as a manure spreader, which as its name implies is used to spread barnyard manure. In a typical farm operation, manure is dispensed in fields for the purpose of conveniently disposing of accumulated manure as well as providing nutrients that enhance the characteristics of the soil in which crops are to be grown. To this end, a variety of manure spreaders have been developed over the years to haul and distribute different types of manure. For instance, conventional box spreaders are preferred for handling dry, clumpy types of manure.
Box spreaders comprise a box-like holding container in which a moveable conveyor is mounted in the bottom for transferring the material to the rear of the container. Rotating beaters, typically paddle shaped, are mounted in a transverse fashion at the rear of the container to engage and break up the material that has been conveyed rearwardly. The paddles also serve to distribute the broken up material in a swath behind the spreader as it is transported across the field.
Even though box spreaders have proven to be effective for dry, clumpy manure, they have not been as effective for distributing manure that has a significant liquid content. One problem is that box spreaders are open at the back, and are not normally sealed, resulting in leakage of the liquid content of the manure as it is being transported to the field, which in many instances is over publicly traveled roadways. To overcome this and other problems encountered with respect to the handling of liquid and semi-liquid manure, spreaders have been developed in which the material is held in a leak proof container.
In one common design the container is a V-shaped tank with inwardly angled sides for guiding material, such as manure, to an auger assembly mounted in the bottom. As manure is loaded into the tank onto the auger assembly, it engages it and conveys it to an expeller assembly for discharge from the tank. This type of spreader, as opposed to a box spreader, is commonly referred to as a tank spreader and is well adapted for handling cattle manure in liquid or slurry form as well as other types of manure with a lesser liquid content, such as swine and poultry manures.
In tank type spreaders, there are various arrangements employing either one or two augers for moving material to a discharge area. A typical example of a single auger machine is shown in U.S. Pat. No. 5,221,049, issued Jun. 22, 1993 in the name of Gilbert W. Linde, et al, while, on the other hand, U.S. Pat. No. 5,386,943, issued Feb. 7, 1995 in the name of a Kenneth J. Peeters, shows a two auger arrangement. In the latter patent a spreader is depicted in which a transverse beater is mounted above the augers to engage material as it is urged rearwardly by the augers to an external transverse beater type expeller.
U.S. Pat. Nos. 5,199,638, issued Apr. 6, 1993 in the name of Thomas R. Fischer, and U.S. Pat. No. 5,275,335, issued Jan. 4, 1994 in the name of Stanley W. Knight, et al, are also directed to dual auger machines. In the spreaders shown in these two patents the augers, rotating in the same direction, are utilized in a cooperative manner to convey material to a side discharge assembly. In the '335 patent one auger is mounted above the other, while in the '638 patent the augers are mounted in a side-by-side fashion at the same elevation, and in both instances feed assist means are provided for conveying the manure to a side delivery discharge area.
Still another dual auger machine representative of the prior art is shown in U.S. Pat. No. 5,435,494, issued Jul. 25, 1995 also in the name of Stanley W. Knight, et al. In the several embodiments of the '494 machine one of the augers is used as a feed auger and the other is used as a discharge auger. The manure is conveyed to discharge means, comprising one or two side delivery assemblies, or an end mounted assembly.
In another prior art arrangement for tank spreaders side discharge is not used. Dual augers convey material to rearwardly located expellers rotated about one or more horizontal axes. Exemplary of this combination are U.S. Pat. No. 3,781,588, issued Mar. 18, 1975 in the name of John B. Long, et al, U.S. Pat. No. 4,124,166, issued Nov. 7, 1978 in the name of Gustave Lucas, and U.S. Pat. No. 4,801,085, issued Jan. 31, 1989 in the name of Thomas R. Fischer.
In yet another arrangement where side discharge is not used, the expeller is mounted to rotate about a vertical axis. Typical of this latter arrangement, is U.S. Pat. No. 5,501,404, issued Mar. 26, 1996 in the name of Donald A. Meyer, et al, which in the principal embodiment shows rotary expeller means with blades extending from a vertical shaft mounted rearwardly and external of the tank. Another example of a vertical expeller arrangement is shown in U.S. Pat. No. 2,296,909, issued Sep. 29, 1942 in the name of Merrills L. Dake, showing a truck mounted spreader used for spreading granulated material, such as salt, sand, or the like. In this spreader the augers, mounted within a flat bottomed tank, are counter rotating to discharge the material through an opening in the back wall of the tank onto distribution discs rotating about vertical shafts.
Notwithstanding the numerous kinds of spreaders available for transporting and discharging material such as manure, a problem commonly encountered, particularly in side delivery spreaders, is uneven discharge. This is especially prevalent in tank type manure spreaders designed to handle slurry material having a high liquid content. Typically the material delivered to the field is more heavily concentrated near the expeller, i.e., in the vicinity of the path of the spreader as it traverses the field on which material is being discharged. An attempt to solve this problem by increasing the speed of the expeller merely tends to shift the entire spread pattern further away from the path of the spreader. The uneven pattern continues to exist, i.e., the heavy concentration is merely further away from the spreader, and thus this arrangement still fails to provide even distribution throughout the pattern.